6. Troubleshooting (22%)
Troubleshooting is the domain that separates candidates who have absorbed the prior phases from those who merely memorized them. Every other phase is knowledge; this phase is application. The exam presents broken systems and asks you to diagnose them — using the same methodology a real administrator would. The process isn't guesswork; it's systematic elimination.
The mental model for this phase: troubleshooting is a diagnostic algorithm, not a series of random attempts. Define the problem precisely → gather data → form a hypothesis → test it → conclude. Skipping to solutions without gathering data is how administrators spend four hours "fixing" the wrong thing.
⚠️ Common Misconception (M10): High CPU usage is not the same as CPU being the bottleneck. A process showing 90% CPU might be doing useful work efficiently. The question is: is CPU wait high (processes queued for CPU) or is I/O wait high (CPU idle but waiting for disk/network)? vmstat's wa column and mpstat's %iowait answer this. Confusing symptom with root cause is the #1 diagnostic error.
